Effects of restricted sleep with different exercise loads upon subsequent sleep

Seven male cats were adapted to different schedules of restricted sleep. The cat was permitted to go to sleep either 2, 4 or 8 hours per day with the balance to 24-h periode spent in wakefulness enforced by means of a treadmill. Two experiments were run and the same cats served in both runs. The experiments and schedules were separated by at least two weeks during which time cats were maintained under ordinary laboratory conditions. Our experiment used treadmill speed of 2.6 m/min which was easily tolerated and effective in eliminating sleep. Another experiment used treadmill speed of 4.6 m/min which produced more physical exercise. As available sleep time become progressively shorter, REM sleep increased while SWS decreased. If restriction in sleep time was associated with more physical exercise then the composition of the subsequent sleep was different : SWS increased while REM sleep decreased. The functional significance of these opposite effects are presumably different. The immediate SWS response to the prior muscular exercise is suggestive of its recovery function.     

Effects of exhaustive submaximal exercise on cardiovascular function during sleep

The influence of an afternoon bout of exhaustive submaximal exercise on cardiovascular function and catecholamine excretion during sleep was examined in five female and four male subjects. Subjects walked on a treadmill for successive 50-min periods at 50, 60, and 70% maximal O2 consumption, separated by 10-min rest periods. Exercise terminated with volitional exhaustion. Following an adaptation night, electroencephalographic and impedance cardiographic measures were obtained during three successive nights of sleep, with exercise preceding night 3. Relative to the base-line night (night 2), exhaustive exercise resulted in a sustained elevation of heart rate and cardiac output throughout the entire night's sleep. The magnitude of these elevations was unaffected by sleep stage but decreased over the night. The typical pattern of circadian decline in cardiac output was unaltered. However, the decline in heart rate with sleep onset was greater on the exercise night. Changes in impedance dZ/dt and R-Z interval suggested an enhanced myocardial contractility during the first 3 h of sleep postexercise. Analysis of morning urine samples revealed that in seven of nine subjects norepinephrine excretion increased, epinephrine excretion decreased, and dopamine excretion was unchanged during sleep on the exercise night. It is suggested that these cardiac changes reflect a sustained increase in myocardial beta-receptor activity.     

Effects of partial sleep deprivation after prolonged exercise on metabolic responses and exercise performance on the following day

[Purpose]We determined the effect of partial sleep deprivation (PSD) after an exercise session on exercise performance on the following morning.[Methods]Eleven male athletes performed either a normal sleep trial (CON) or a PSD trial. On the first day (day 1), all subjects performed an exercise session consisting of 90 min of running (at 75% V˙O2max) followed by 100 drop jumps. Maximal strength (MVC) was evaluated before and after exercise. In the CON trial, the sleep duration was 23:00–7:00, while in the PSD trial, the sleep duration was shortened to 40% of the regular sleep duration. On the following morning (day 2), MVC, the metabolic responses during 20 min of running (at 75% V˙O2max), and time to exhaustion (TTE) at 85% V˙O2max were evaluated.[Results]On day 2, neither the MVC nor V˙O2 during 20 min of running differed significantly between the two trials. However, the respiratory exchange ratio was significantly lower in the PSD trial than in the CON trial (p = 0.01). Moreover, the TTE was significantly shorter in the PSD trial than in the CON trial (p = 0.01).[Conclusion]A single night of PSD after an exercise session significantly decreased endurance performance without significantly changing muscle strength or cardiopulmonary response.     

Effects of exercise with or without light exposure on sleep quality and hormone reponses

[Purpose]

The objectives of the present study were to determine the effect of sun exposure and aerobic exercise on quality of sleep and investigate sleep-related hormonal responses in college-aged males.

[Methods]

In this study, the cross-over design was utilized. The subjects (N = 10) without any physical problems or sleep disorders participated in the experimental performed 4 protocols in only sun exposure (for 30 minutes, EG1) protocol, only aerobic exercise (walking and jogging for 30 minutes, EG2) protocol, aerobic exercise with sun exposure (EG3) protocol, and control (no exercise and no sun exposure, EG4) protocol. Each protocol was 5 times per week with one-week break (wash-out period) between protocols to prevent the effects of the previous protocol. Total test period was should be 7 weeks (one week of protocol and one week of break). Before and after each aerobic exercise session, the subjects completed stretching to warm up for 5 to 10 minutes. Surveys consisting of (bedtime, wake-up time, sleep onset latency, and (Pittsburgh Sleep Quality Index (PSQI) were obtained before the test and after each protocol. After each protocol, the following sleep-related hormonal responses were measured: blood concentrations of melatonin, cortisol, epinephrine, and norepinephrine. One-way ANOVA was used to determine differences between protocols. Statistical significance was set at p < 0.05.

[Results]

Bedtime of EG4 was significantly later than that of the EG1 or EG3. Wake-up time in the EG4 was significantly later than that of the EG1 or the EG3. Sleep onset latency in the EG4 was longer than that of the EG3. The quality of sleep in the EG4 was lower than that of the EG3. Sleep cycle in the EG4 was significantly shorter than that of the EG1. Blood melatonin concentrations of the EG3 was significantly higher than that of the EG4. There were no significant differences in blood concentrations of cortisol, epinephrine, or norepinephrine among protocols, with the order from the lowest to the highest values of EG1 < EG2 < EG3 < EG4.

[Conclusion]

The present data found that EG1 and EG3 showed positive sleep-related hormonal responses, sleep habits, and quality of sleep, indicating that sun exposure or exercise with sun exposure may improve the physical status and quality of life.     

Epidemiology of exercise and sleep

Sleep and Biological Rhythms - Although exercise is widely believed to improve sleep, experimental evidence has found acute and chronic exercise to exert only modest effects on subsequent sleep....     

Effects of exercise on insulin-induced hypoglycemia

The purpose of this study was to determine the effect of exercise on the rate of onset of hypoglycemia induced by infusion of excess insulin (0.8 mU.min-1.100 g-1). Rats were either fasted overnight (FS) or fed ad libitum (FD). FS rats were killed after 5, 10, or 15 min of infusion at rest or after running on the treadmill at 21 m/min and 15% grade. FD rats were killed after 10, 20, or 40 min of infusion at rest or after exercise. Rats were also killed 15 min postexercise for FS and 60 or 120 min postexercise for FD with continued insulin infusion. The progressive decline in blood glucose was not altered by exercise in the FS rats. FD rats showed a significant difference due to exercise only after 40 min (rest 4.2 +/- 0.3 mM, exercise 3.2 +/- 0.2 mM). A significant postexercise repletion of glycogen was observed in red vastus and soleus muscles of FD rats despite the decreasing blood glucose values. These data indicate that exercise accelerates the rate of development of hypoglycemia in FD rats. In the FS rats, where the rate of decline in blood glucose was greater, exercise had no effect on the time course of development of hypoglycemia.     

Effects of naloxone on exercise performance

This study was designed to investigate the effects of naloxone on athletic performance in humans. Two groups of elite middle-distance runners performed a maximal or a submaximal exercise protocol following the double-blind intravenous injection of either naloxone (0.15 mg X kg body wt-1) or saline. The maximal test (group M) was comprised of a short-duration treadmill run to maximal intensity; the submaximal test (group S), a prolonged submaximal treadmill run to exhaustion. O2 uptake, heart rate, ventilation, and perceived exertion were determined during each test. Perception of pain was assessed after exercise by use of a modified McGill pain questionnaire. No significant differences between placebo and naloxone treatments were found in any of the measured variables at the usually accepted 5% (P = 0.05) confidence level; however, evidence suggesting differences (i.e., P = 0.1 to 0.05) in these important respects was observed. In group M, maximal exercise performance measured by maximal O2 consumption was not different between placebo and naloxone; results suggest that VE was increased (P = 0.08) following naloxone, but only at the final work stage. In group S, exercise performance time was reduced following naloxone (P = 0.09), whereas the affective component of pain was increased (P = 0.06); no differences in the measured physiological variables were observed. These results suggest the following: 1) the opiate receptor-endorphin system may alter the perception of pain associated with prolonged high-intensity submaximal exercise with a resultant significant effect on performance; and 2) it may play a role in the control of ventilation during maximal exercise.     

Effects of exercise order on upper-body muscle activation and exercise performance

With the purpose of manipulating training stimuli, several techniques have been employed to resistance training. Two of the most popular techniques are the pre-exhaustion (PRE) and priority system (PS). PRE involves exercising the same muscle or muscle group to the point of muscular failure using a single-joint exercise immediately before a multi-joint exercise (e.g., peck-deck followed by chest press). On the other hand, it is often recommended that the complex exercises should be performed first in a training session (i.e., chest press before peck-deck), a technique known as PS. The purpose of the present study was to compare upper-body muscle activation, total repetitions (TR), and total work (TW) during PRE and PS. Thirteen men (age 25.08 +/- 2.58 years) with recreational weight-training experience performed 1 set of PRE and 1 set of PS in a balanced crossover design. The exercises were performed at the load obtained in a 10 repetition maximum (10RM) test. Therefore, chest press and peck-deck were performed with the same load during PRE and PS. Electromyography (EMG) was recorded from the triceps brachii (TB), anterior deltoids, and pectoralis major during both exercises. According to the results, TW and TR were not significantly different (p > 0.05) between PRE and PS. Likewise, during the peck-deck exercise, no significant (p > 0.05) EMG change was observed between PRE and PS order. However, TB activity was significantly (p < 0.05) higher when chest press was performed after the peck-deck exercise (PRE). Our findings suggest that performing pre-exhaustion exercise is no more effective in increasing the activation of the prefatigued muscles during the multi-joint exercise. Also, independent of the exercise order (PRE vs. PS), TW is similar when performing exercises for the same muscle group. In summary, if the coach wants to maximize the athlete performance in 1 specific resistance exercise, this exercise should be placed at the beginning of the training session.     

Stress hormonal response to exercise after sleep loss

While prolonged loss of sleep is unpleasant and demanding, it remains unclear if it blunts or enhances the physiological stress imposed by subsequent exercise. To investigate this, we deprived eight subjects of sleep prior to exercise to see if this altered the stress hormonal response to that exercise. In a first series of experiments, two fragmented nights of sleep preceded 30 min of heavy treadmill walking exercise. While sleep loss disturbed mood before and during exercise (p less than 0.05), it left stress hormonal levels (cortisol and beta-endorphin) in blood identical to control. In a second series, subjects performed light treadmill walking exercise for 3 h after 36 sleepless hours. As before, sleep deprivation disturbed mood before and throughout exercise (p less than 0.05), but failed to change blood levels of stress hormones. In both series, sleeplessness left heart rate, oxygen uptake, minute ventilation, and body core temperature unchanged in exercise. We conclude that sleep loss provokes psychological changes during subsequent exercise without measurably altering the stress hormonal response to that exercise.     

Effects of sleep deprivation on respiratory events during sleep in healthy infants

This study was designed to determine the effects of sleep deprivation on respiratory events during sleep in healthy infants. Ten unsedated full-term infants (1-6 mo) were monitored polygraphically during "afternoon naps" on a control day and on the day after sleep deprivation. Respiratory events, i.e., central apnea, obstructive apnea and hypopnea, and periodic breathing were tabulated. Results for respiratory events were expressed as 1) indexes of the total number of respiratory events and of specific respiratory events per hour of total sleep (TST), "quiet" sleep (QS) and "active" sleep (AS) times; 2) total duration of total and specific respiratory events, expressed as a percentage of TST, QS, and AS times. After sleep deprivation, significant increases were observed for 1) respiratory event (P less than 0.001), central apnea (P less than 0.05), and obstructive respiratory event (P less than 0.01) indexes; 2) respiratory event time as a percentage of TST (P less than 0.002) and as a percentage of AS time (P less than 0.001); 3) obstructive respiratory event time as a percentage of TST (P less than 0.01), QS (P less than 0.05), and AS times (P less than 0.002). The present study shows that short-term sleep deprivation in healthy infants increases the number and timing of respiratory events, especially obstructive events in AS.     

Effects of exercise on longevity of rats

It has been postulated that life span is inversely related to energy expenditure. If this is correct, regularly performed exercise could accelerate the aging process. In two early studies, exercise shortened the life span of rats; the results of these studies have been cited as evidence for the concept that an increase in energy expenditure accelerates aging. However, subsequent studies have not confirmed this finding. Instead, the weight of evidence now indicates that rats that exercise regularly have a longer average life span than sedentary, ad libitum-fed controls. Freely eating sedentary rats become obese, indicating that their food intake is in excess of their energy requirements. Available evidence seems compatible with the interpretation that exercise results in improved survival in rats by countering deleterious effects of a sedentary life combined with overeating.     

Effects of exercise and lack of exercise on insulin sensitivity and responsiveness

Insulin action is enhanced in people who exercise regularly and vigorously. In the present study, the hyperinsulinemic, euglycemic clamp procedure was used to determine whether this enhanced insulin action is due to an increased sensitivity and/or an increased responsiveness to insulin. To avoid the variability that exists between individuals and complicates cross-sectional studies, the same subjects were studied in the trained exercising state and again after 10 days of physical inactivity. When the plasma insulin concentration was maintained at approximately 78 microU.ml-1 (a submaximal level), glucose disposal rate averaged 8.7 +/- 0.5 mg.kg-1.min-1 before and 6.7 +/- 0.6 mg.kg-1.min-1 after 10 days of activity (P less than 0.001). When the plasma insulin concentration was maintained at approximately 2,000 microU.ml-1 (a maximally effective concentration), the rate of glucose disposal was not significantly different before (15.3 +/- 0.5 mg.kg-1.min-1) compared with after (14.5 +/- 0.4 mg.kg-1.min-1) 10 days without exercise. These results provide evidence that the reversal of enhanced insulin action that occurs within a few days when exercise-trained individuals stop exercising is due to a decrease in sensitivity to insulin, not to a decrease in insulin responsiveness.     

Effects of exercise training on alpha-motoneurons.

Evidence is presented that one locus of adaptation in the "neural adaptations to training" is at the level of the alpha-motoneurons. With increased voluntary activity, these neurons show evidence of dendrite restructuring, increased protein synthesis, increased axon transport of proteins, enhanced neuromuscular transmission dynamics, and changes in electrophysiological properties. The latter include hyperpolarization of the resting membrane potential and voltage threshold, increased rate of action potential development, and increased amplitude of the afterhyperpolarization following the action potential. Many of these changes demonstrate intensity-related adaptations and are in the opposite direction under conditions in which chronic activity is reduced. A five-compartment model of rat motoneurons that innervate fast and slow muscle fibers (termed "fast" and "slow" motoneurons in this paper), including 10 active ion conductances, was used to attempt to reproduce exercise training-induced adaptations in electrophysiological properties. The results suggest that adaptations in alpha-motoneurons with exercise training may involve alterations in ion conductances, which may, in turn, include changes in the gene expression of the ion channel subunits, which underlie these conductances. Interestingly, the acute neuromodulatory effects of monoamines on motoneuron properties, which would be a factor during acute exercise as these monoaminergic systems are activated, appear to be in the opposite direction to changes measured in endurance-trained motoneurons that are at rest. It may be that regular increases in motoneuronal excitability during exercise via these monoaminergic systems in fact render the motoneurons less excitable when at rest. More research is required to establish the relationships between exercise training, resting and exercise motoneuron excitability, ion channel modulation, and the effects of neuromodulators.